What are the causes and management of Irritable Bowel Syndrome (IBS)?

Causes and Management of Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) is primarily caused by altered gut-brain interaction, with key contributing factors including psychological stress, visceral hypersensitivity, post-infectious inflammation, and food intolerances. 1

Causes of IBS

Primary Pathophysiological Mechanisms

• Altered Gut-Brain Interaction

  • Bidirectional communication disturbance between gut and brain 1
  • Abnormal central nervous system processing of visceral pain 1
  • Visceral hypersensitivity (heightened pain perception in the gut) 1

• Psychological Factors

  • Psychological stress is a major trigger for symptom flares 2
  • 50% of hospital outpatients attribute symptom onset to stressful events 1
  • Anxiety and depression affect up to one-third of IBS patients 1
  • History of childhood or adult sexual/physical abuse reported in one-third of patients 1

• Post-Infectious Inflammation

  • 10-20% of patients develop IBS following acute gastrointestinal infection 1
  • Low-grade mucosal inflammation from compromised epithelial barrier 1
  • Increased mast cells in the colon, particularly in descending and rectosigmoid regions 1

• Transit and Motility Abnormalities

  • Abnormal colonic transit in 10-20% of IBS-C and 25-45% of IBS-D patients 1
  • Altered serotonin (5-HT) metabolism affecting gut motility 1
  • High 5-HT levels in IBS-D, low levels in IBS-C 1

• Dietary Factors

  • Food intolerances reported by many patients 1
  • Common intolerances: wheat, dairy products, coffee, potatoes, corn, and onions 1
  • Lactose intolerance found in 10% of IBS patients 1

Diagnosis of IBS

Diagnostic Criteria

• Rome Criteria (most recent version preferred)

  • Recurrent abdominal pain associated with defecation or change in stool frequency/form 1
  • Symptoms present for at least 6 months 3

• Manning Criteria

  • Six key symptoms including pain relief with defecation, looser/more frequent stools with pain onset, abdominal distension, mucus passage, and sensation of incomplete evacuation 1

Diagnostic Approach

• Positive diagnosis based on symptom criteria rather than extensive testing 4
• Testing to exclude celiac disease is recommended 4
• Limited investigation when typical symptoms present with:
  • Normal physical examination
  • Absence of alarm features (weight loss, rectal bleeding, nocturnal symptoms, anemia) 1
  • Age <45 years 1

Management of IBS

Dietary Interventions

• First-line: Traditional dietary advice 4

  • Identify and limit trigger foods
  • Regular meal patterns
  • Adequate fluid intake

• Second-line: Low FODMAP diet for moderate to severe symptoms 5

  • Implementation under supervision of trained dietitian 5
  • Elimination phase followed by structured reintroduction

• Fiber supplementation

  • Soluble fiber (e.g., psyllium) beneficial for overall symptoms 4
  • Avoid insoluble fiber which may worsen symptoms 5

Pharmacological Management

1. For IBS with Constipation (IBS-C)

   • First-line: Osmotic laxatives 5
   • Second-line: Secretagogues (lubiprostone 8mcg twice daily) 3
   • Lubiprostone showed 14% response rate vs 8% for placebo in clinical trials 3

2. For IBS with Diarrhea (IBS-D)

   • First-line: Anti-diarrheal medications 4
   • Second-line: 5-HT3 antagonists, eluxadoline, or rifaximin 4

3. For Abdominal Pain

   • First-line: Antispasmodics 4
   • Second-line: Gut-brain neuromodulators 4
   • Low-dose tricyclic antidepressants (e.g., amitriptyline 10-50mg at bedtime) preferred 5, 4

Psychological Interventions

• Brain-gut behavioral therapies (BGBTs) are effective, especially for refractory cases 4

  • Cognitive behavioral therapy
  • Gut-directed hypnotherapy
  • Mindfulness-based stress reduction 5

• Psychological therapy indications:

  • Moderate to severe symptoms
  • Patient acceptance of gut-brain connection
  • Inadequate response to conventional treatments 5

Common Pitfalls and Caveats

1. Misdiagnosis

   • IBS is a diagnosis of inclusion based on specific criteria, not exclusion 1
   • Avoid excessive, costly investigations in typical cases without alarm features

2. Overlooking Psychological Factors

   • Psychological comorbidity significantly impacts quality of life and treatment outcomes 1
   • Addressing psychological aspects is essential for comprehensive management

3. Medication Overuse

   • Avoid opioid analgesics for pain management as they worsen GI dysmotility 5
   • Long-term use of certain antibiotics (e.g., metronidazole) can cause peripheral neuropathy 5

4. Inadequate Follow-up

   • Review treatment efficacy after 3 months
   • Discontinue ineffective medications rather than continuing indefinitely 5

5. Unrealistic Expectations

   • Set realistic goals for symptom improvement rather than complete resolution
   • Emphasize long-term management strategies over "quick fixes"

By understanding the complex interplay of factors causing IBS and following a structured management approach targeting specific symptoms, patients can achieve significant improvement in both symptoms and quality of life.